The present invention relates to a device for automatically detecting the dynamic out-of-balance condition of a rotor or the like and correcting it.
In the rotary machine, a rotor must be correctly dynamically balanced in order to prevent vibration, noise and degradation of performance and durability. However, it has been extremely difficult to attain the realization of this process, e.g. the automatic (to be referred to as "out-of-balance" in this specification for brevity) detection and correction of the dynamic out-of-balance condition.
So far only the step for detecting the out-of-balance condition of a rotor or the like has been automated, and correction has been manually carried out so that the balancing efficiency is low, the rotor cannot be balanced with a high degree of accuracy, and skilled workers are required.
Recently rotor balancing devices utilizing non-contacting machining techniques such as laser beam have been devised and demonstrated, but their performance has not been satisfactory in practice because of the below described problems. In general, as compared with the latent heat of heating and melting, the latent heat of evaporation of metal is considerably higher, and the evaporation and removal of excess metal is used in balancing a rotor so that the prior art devices for utilizing only the thermal energy liberated by the laser beam for evaporating metal have low efficiency and are not economical. The present day laser technique provides pulsed laser beam which has a thermal energy of only a few joules per pulse when pulsated at a high repetition rate so that only a few micrograms of metal may be evaporated and removed per pulse. However, in order to balance a rotor of even a small-sized motor about one gram of metal must be evaporated and removed.
Therefore with the prior art balancing devices of the type utilizing the noncontacting machining techniques such as using laser beam, very minute parts such as those of wrist watches and rotors such as those of gyroscopes which must be balanced with a higher degree of accuracy may be advantageously balanced, but rotors of motors of the general type cannot be balanced economically.